Grinding apparatus primarily for lignocellulose containing material



June 6, 1967 P D ETAL 3,323,731

GRINDING APPARATUS PRIMARILY FOR LIGNOCELLULOSE CONTAINING MATERIAL 2Sheets-Sheet 1 Filed June 22, 1964 June 6, 1967 J ASPLUND ETAL 3,323,731

' GRINDING APPARATUS PRIMARILY FOR LIGNOCELLULOS CONTAINING MATERIALFiled June 22, 1964 2 Sheets-Sheet 2 V/l/ I. I .21 I

xzzo

United States Patent 3,323,731 GRINDING APPARATUS PRIMARILY FGR LEGNO-CELLULOSE CONTAINEN G MATERIAL Arne Johan Arthur Asplund and RoifBer-til Reinhail,

Lidingo, and Johan Gunnar Inge Johansson, Nasbypark, Sweden, assignorsto Defibrator Aktieholag, Stockholm, Sweden, a corporation of SwedenFiled June 22, 1964, Ser. No. 376,779 Claims priority, applicationSweden, July 1, 1963, 7,303/63 7 Claims. (Cl. 241-146) This inventionrelates to grinding apparatus.

More particularly this invention relates to a grinding apparatus,primarily intended for lignocellulose containing material and providedwith two rotatable grinding dis-cs disposed within a casing and eachco-operating with a stationary grinding disc, inlet and dischargechannels for the material to be treated being provided in the casing foreach pair of co-operating grinding discs.

A grinding apparatus of this type can be given the double capacitycompared with that of an apparatus with one pair only of co-operatinggrinding discs.

One main object of the invention is to provide an improvement of thistype of grinding apparatus, denominated also as double grinders so as topermit to adjust the two pairs of grinding discs to the same ordifferent grinding pressures irrespective of whether the channels or thepaths of flow pertaining to them are coupled in parallel or in series. 7

A further object of the invention is to provide an improvement of thegrinding apparatus in consideration, which renders possible anadjustment of the grinding pressure between the two pairs of grindingdiscs from a position where only one pair is in operation to a positionwhere both pairs are loaded equally, and to all conceivable intermediatepositions between said limits.

Further objects and advantages of the invention will become apparentfrom the following description considered in connection with theaccompanying drawings, which form part of the specification and ofwhich:

FIG. 1 is a vertical longitudinal section through a grinding apparatusconstructed according to the invention.

FIG. 2 is a sectional view of the central part of the apparatus with thepaths of flow pertaining to the pairs of grinding discs coupled inparallel to one another.

FIG. 3 is the same sectional view but with the paths of flow disposed inseries.

Referring to the drawings, reference numeral denotes a stationary basestructure of the apparatus to which horizontally divided casings orhousings 11, 12 and 13, 14 respectively, are connected. A shaft 16passes through the casings and is at its one end mounted in a bearing 18which preferably is of anti-friction or roller type and which is capableof absorbing beside radial thrust, also axial thrust in both directions.The two casings are separated from one another by a part 20 of the basestructure 10, which on either side supports a stationary grinding disc22, 24, respectively. Rigidly secured to the shaft 16 is a grinding disc26 rotating with said shaft and which together with the stationary disc22 forms a grinding interspace 28, through which the material to bedisintegrated therein is passed in an upward direction.

The shaft 16 on the opposite side of the casings 11, 12 and 13, 14,viewed from the bearing 18, is concentrically surrounded by a tubularshaft 30 which is slidably supported by a radial thrust bearing 39,preferably a spherical roller bearing. Disposed between the shafts 16and 30 are splines 34 so that said shafts are axially displaceablerelatively to one another but rotate together, the outer shaft through acoupling 36 being connected to a driving motor (not shown). The shaft 30carries a grind- Patented June 6, 1967 ing disc 38 rigidly anchoredthereon and co-operating with the stationary grinding disc 24, agrinding interspace 40 being formed therebetween and through which thematerial to be treated is passed in a radial outward direction wherebythis material becomes finely divided or disintegrated.

The material to be ground is supplied to the pairs of grinding discs 22,26 through a channel 42 which may extend in the base part 20 to acentral space 44 adjacent the inner faces of said grinding discs. Thepulp ground between them is discharged through a channel 46. In the samemanner, the other pair of grinding discs 24, 38 has a supply channel 48in the base part 20 which opens into a space 50 formed centrally insidesaid grinding discs. The pulp ground between said discs is dischargedthrough a channel 52. The channels 46, 52 are located in the casings'1-1, 12 and 13, 14 enclosing the grinding discs.

The parts of the radial and axial thrust bearing 18 not participating inthe rotation are enclosed by a ring member 54 formed with a cylindricexternal face which is axially slidable on a corresponding formed faceof a casing 56 rigidly secured onto the base structure 10. Connected tothe ring member '54 is a disc 58 and to the latter a servo-motor piston60 which has an outer annular flange 62 adapted to be displaced axiallyWithin a prolongation 64 of the casing 56. Formed on either side of theflange 62 is a chamber 66, 68 respectively adapted to be connected to apressure source or an outlet in a manner to be described later more indetail.

The supply of pressure fluid to the servo-motor 60, 64 is controlled bya pilot valve generally denoted and of the type known per se as isdisclosed, for instance, by the patent specification No. 2,997,704. Thepilot valve 30 is rigidly connected with the prolongation 64 of thecasing 56 of the servo-motor 60, 62. The pilot valve includes a pistonor valve body 82 formed with a central flange S3 and two lateral flanges84, 85. The pilot valve 80 has a central chamber 86 and two lateralchambers 87, 88. Between the two lateral chambers 87, 88 and the centralchamber 86, the inner diameter of the valve housing is reduced tocorrespond to the external diameter of the flanges. The flange 83 has anaxial dimension which, by a small unit of measure, such as of onehundredth or a few hundredths of one millimetre, is shorter than thelength of the chamber 86. In the same manner the flanges '84, have anaxial dimension which is only slightly less than the length of thechambers 87, 88. In the middle position all flanges are positioned rightin front of their pertaining chambers.

A pipe 89 connects the central chamber 86 of the pilot valve with an oilsump 90, a pump 91 being provided in this pipe and a spring-loaded valve93 in a return pipe 92 connected to said pipe 89. From a space 94,having the reduced diameter corresponding to that of the flanges of thevalve body 82 and located between the chambers 86 and 87 of the pilotvalve 80, a pipe 95 extends to the chamber 68 on one side of the flange62 of the servomotor. A pipe 96 connects a space 97 with the samereduced diameter of the pilot valve located on the other side of thecentral chamber 86 with the chamber 66 on the opposite side of theflange 62. Through a return pipe 98 the lateral chambers 87, 88 are inopen connection with the sump 90.

An adjustment screw 100 is passed through a threaded passage in an arm99 fixed to the servo-motor piston 64 said adjustment screw beingcoaxial with the valve body 82 of the pilot valve and adapted to act onthe facing end of said valve body projecting from the valve casing. Theother end of the valve body 82 is under the load of a spring member 101tending always to keep the valve body pressed against the adjustmentscrew 160.

Another pilot valve 102 has for its object to control the supply ofpressure fluid to the servo-motor 70, 72. This pilot valve is of thesame construction as the pilot valve 80. In FIG. 1 the same referencenumerals have been used for both servo-motors with the addition of asufiix for the pilot valve 102. The casing thereof is fixed in the basestructure 10. The arm 104 carrying the adjustment screw 100 is fixed ina ring member 106 surrounding the nonrotating part of the bearing32. Thering member 106 is axially displaceable within a surrounding stationaryouter casing 180 and due to this feature follows the shaft 30 in theaxial movements thereof.

Extending from the chamber 94 of the pilot valve 102 is a pipe 110 whichis extended to the outer end of the hollow servo-motor piston 60 andhere connected to a pipe 112 extending through the piston 60 and theshaft 16 to the chamber 78.

As shown in FIG. 2 the grinding apparatus may be adjusted so that theboth pairs of grinding discs 22, 26 and 24, 38, respectively, operate inparallel with two fractions of pulp or material to be ground. The onefraction or stream of pulp is introduced through the channel 42 and thechamber 44, and passes radially outwards between the grinding discs 22,26 while a disintegration of fibre bundles or fibres is effected. Theground pulp is discharged through the outlet 46. The other fraction orstream of pulp passes through the channel 48, the chamber 50, and theinterspace between the discs 24 and 38 and is discharged through theoutlet 52. In the two fractions the quality of the material to betreated may be dilferent prior to and/ or after the grinding operationdepending on the conditions.

Disposed inthe inlet and outlet channels may be locking and/ orcontrolling or regulating valves 120, 122, 124 and 126.

The two pairs of grinding discs may also operate in series which meansthat they may be passed by the same stream of material to be treated inthe apparatus. For this purpose the channel 46 is connected with thesupply channel 48 by means of a connecting pipe branch or coupling 128,the valve 124 and possibly also the valve 122 being dispensed with.After the pulp fed through the channel 42 has been subjected to agrinding treatment in a first step between the discs 22, 26, it isconveyed over to the internal space between the second pair of grindingdiscs 24, 38 where a grinding treatment in a second step is carried outon the pulp which then will be discharged through the channel 52.

According to the invention, it is possible in both cases to adjust thepressure in the interspace between the two pairs of discs 22, 26, and24, 38 respectively, or the width of the interspaces 28, 40 within thewidest limits by means of the two servo-motors. Assuming that the piston82 of the pilot valve 80 takes such position that pressure fluid issupplied through the pipe 96 to the chamber 66, the servomotor piston 60will then produce over the disc 58, the ring member 54, the axial thrustbearing 18 and the shaft 16, a pressure, which will urge the disc 26towards the stationary disc 22. If, on the other hand, the pressurefluid is fed through the pipe 95 into the chamber 68, pressure thusproduced will urge the disc 38 in a direction towards the disc 24. Ifthe piston 82 of the pilot valve 102 takes such a position that thepressure fluid is supplied through the pipes 114, 116, 118 to thechamber 76 and the second servo-motor, the shaft 16 will be displaced tothe right and V the shaft 30 to the left viewed in the plane of FIG. 1,

which implies that the two grinding discs 26, 38 are urged in adirection towards the respective stationary discs 22 and 24. Thepressure becomes equally great in the two 4 quently the width of theinterspace 28, 40, are regulated by adjusting the pistons 82, 82relatively to the stationary casing of the pilot valves 80, 102, whichin the embodiment shown, is effected by means of the adjustment screws100, 100 respectively. When the predetermined grinding interspaceprevails, the pistons 82, 82 of the two pilot valves assume anintermediate position. With regard to the servo-motors 60, 64, thisresults in that the same pressure prevails in the two chambers 66, 68.If the interspace 28 between the discs 22, 26 is increased due to, forinstance, increased supply of material to be ground, the piston 60 ofthe servo-motor is forced to the left, as will be easily understood,thus moving the arm 99.'The valve piston 82 follows with the servo-motorpiston due to action of the spring 101. The chamber 97 is now connectedwith the chamber 86, which latter is under the pressure created by thepump 91. Instead, the pressure in the chamber 68 of the servo-motordrops as a consequence of a interspaces 28, 40 and is otherwise absorbedwithin the rotating system and the stationary central base part 20 ofthe base structure. The axial thrust bearing 18 is totally relieved fromthrust. By supplying pressure fluid to the chamber 78 of the servo-motor70, 72 both rotating grindcommunication being established in the pilotvalve between the portion 94 and the chamber 87 which is withoutpressure. The result will be that the servo-motor piston 60 is subjectedto a pressure forcing it to the right, causing the disc 26 to be movedcloser to the disc 22 and thus the predetermined Width of the interspace28 Will be restored.

If, instead, the shaft 16 is displaced to the right, for instance, dueto the stream of pulp passing through the interspace 28 being reducedfor some reason, the pilot piston 82 is moved in the same direction. Theresult will be that pressure fluid is forced from the pump 98 throughthe chambers 86, 94 to the chamber 68 of the servomotor 60, 64. Theshaft 16 moves'nowto the left so that a metallic contact between thegrinding discs is avoided.

The description applies also to the pilot valve'102. The pilot piston 82follows'the axial movements of the shaft 130 through intersection of thearm 104, the ring member .106 and the bearing 32. At the displacement ofthejshaft A 30 and together therewith the piston 82 to the right, a

pressure fluid is fed from the pump 91 through the pipe 89 the chambers86 97 and the pipes 114, 116 and 118 ment screws 100, all conceivablevalues for the grind- 7 ing pressure between the two pairs of grindingdiscs can be created from only one pair being loaded until both areloaded equally. In the same manner the grinding pres.- sures can bevaried in response to all demands set forth regarding the grindingeffect. I I

While one more or less specific embodiment of the invention has beenshown and described, it is to be understood that this is for purpose ofillustration only, and that the invention is not to be limited thereby,but its scope is to be determined by the appended claims.

'What we claim is:

1. A grinding apparatus, primarily intended for lignocellulosecontaining material and provided with two rotatable grinding discsdisposed within a casing and each cooperating with a stationary grindingdisc, inlet and discharge channels for the 'material being provided inthe casing for each pair of co-operating grinding discs. anda.

base structure for said apparatus; characterized in that each of therotating discs is supported by a shaft of which shafts one is positionedconcentrically around the other shaft and which shafts both aredisplaceable axially under 7 the action of pressure fluid actuatedservo-motors.

2. A grinding apparatus as claimed in claim 1, characterized in that oneof the servo-motors has a piston carried by the one shaft and a casingcarried by the other shaft in which casing the piston is axially'displaceable and into which conduits open for supply of pressure fluidto either side of the piston.

3. A grinding apparatus as claimed in claim 2, characterized in that theshaft carrying the piston is at its opposite end, through an axialthrust hearing which is mounted axially movable in the base structure,connected with the piston of the other servo-motor, the casing of whichis fixed to the base structure and has conduits opening on either sideof the last-mentioned piston for supply of pressure fluid to both sidesof the piston.

4. The grinding apparatus as claimed in claim 1, characterized in thatthe two servo-motors are disposed to be actuated each by a pilot valveof a type known per se and controlling the supply of pressure fluid toboth sides of the servo-motor in response to the magnitude of theinterspace between the grinding discs.

5. The grinding apparatus as claimed in claim 1, characterized in thatthe casings are formed for application of the channels in parallelrelation to, or by attachment of a socket, in a series with one another.

6. A grinding apparatus, primarily intended for lignocellulosecontaining material and provided with two rotatable grinding discsdisposed within a casing and each cooperating with a stationary grindingdisc, inlet and discharge channels for the material being provided inthe casing for each pair of cooperating grinding discs, a base structurefor said apparatus; characterized in that the said rotatable discs aresupported by separate shafts, one of said shafts being positionedconcentrically around the other shaft, said shafts being rotatable inone and the same direction, and being displaceable axially under theaction of two servo-motors, one of said servo-motors being adapted toactuate both rotatable grinding discs simultaneously and in oppositedirections, the other servo-motor being adapted to actuate only one ofsaid grinding discs.

7. A grinding apparatus as claimed in claim 6, char acterized in thatone of the servo-motors has a piston carried by one of the shafts and acasing carried by the other shaft in which casing the piston is axiallydisplaceable and into which conduits open for supply of pressure fluidto either side of the piston, said first mentioned shaft being at itsopposite end, through an axial thrust bearing which is mounted axilalymovable in the base structure, connected with the piston of the otherservo-motor, the casing of which is fixed to the base structure and hasconduits opening on either side of the last-mentioned piston for supplyof pressure fluid to both sides of the piston.

References Cited UNITED STATES PATENTS 2,743,874 5/1956 Asplund 241286 X2,864,562 12/1958 Eberhardt et al 241 2,982,482 5/1961 Curtis 241163 XANDREW R. JUHASZ, Primary Examiner.

1. A GRINDING APPARATUS, PRIMARILY INTENDED FOR LIGNOCELLULOSECONTAINING MATERIAL AND PROVIDED WITH TWO ROTATABLE GRINDING DISCSDISPOSED WITHIN A CASING AND EACH COOPERATING WITH A STATIONARY GRINDINGDISC, INLET AND DISCHARGE CHANNELS FOR THE MATERIAL BEING PROVIDED INTHE CASING FOR EACH PAIR OF CO-OPERATING GRINDING DISCS, AND A BASESTRUCTURE FOR SAID APPARATUS; CHARACTERIZED IN THAT EACH OF THE ROTATINGDISCS IS SUPPORTED BY A SHAFT OF WHICH SHAFTS ONE IS POSITIONEDCONCENTRICALLY AROUND THE OTHER SHAFT AND WHICH SHAFTS BOTH AREDISPLACEABLE AXIALLY UNDER THE ACTION OF PRESSURE FLUID ACTUATEDSERVO-MOTORS.
 5. THE GRINDING APPARATUS AS CLAIMED IN CLAIM 1,CHARACTERIZED IN THAT THE CASINGS ARE FORMED FOR APPLICATION OF THECHANNELS IN PARALLEL RELATION TO, OR BY ATTACHMENT OF A SOCKET, IN ASERIES WITH ONE ANOTHER.